Rf Discharge Current And Voltage Measurements and Comparison to an Analytical Model

We have measured the rf current and voltage in a capacitive rf discharge in argon. Along with recent measurements of the electric field in the glow of the discharge, this allows us to determine J .E in the glow, and to compare the power absorption to an analytical discharge model. The discharge is confined within a copper cylindrical enclosure, 23 cm in diameter and 6.4 cm in height. One flat circular side of the enclosure serves as the powered electrode, and the cylindrical side and remaining circular end serve as the ground electrode. The two electrodes are separated by 1 to 2 mm at the rim of the cylinder, and the assembly is placed in a vacuum chamber which serves as the absolute electrical ground. The rf voltage and de bias at the powered electrode are measured with a capacitive divider and low-pass filter, respectively, and the rf current is measured with a Rogowski belt on the grounding strap between the ground electrode and vacuum chamber wall. The current and voltage wave forms are recorded with a gated integrator and boxcar averager module. The power absorbed by the discharge is computed by fourier transforming both wave forms and summing products of the fourier coefficients. These measurements provide data on the variation of current, power, and de bias as the rf amplitude at the powered electrode is varied. Data at 4 mtorr and 20 mtorr, for rf voltage amplitudes of up to 700 V have been acquired.